Field of the Invention
This invention generally relates to a bicycle sprocket and a bicycle crank assembly comprising the bicycle sprocket.
Background Information
Bicycle sprockets are provided both to a crank assembly located in the middle of a bicycle and to the rear wheel, and the rotation of the crank assembly is transmitted to the rear wheel by a chain meshed with the sprockets. In a bicycle chain, an inner link plate and an outer link plate are linked alternately; therefore, when the teeth of the sprockets have the same thickness, the gaps between the outer link plate and the teeth of the sprockets are larger than the gaps between the inner link plate and the teeth of the sprockets. In view of this, there are conventionally known sprockets (Specification of U.S. Pat. No. 4,174,642, for example) in which the axial width of the teeth (the teeth thickness), relative to the rotational center axis direction of the sprocket, is designed such that the axial width of the teeth meshing with the outer link plate is greater than the axial width of the teeth meshing with the inner link plate. A conventional sprocket has teeth that taper diametrally outward. It is thereby unlikely that the gaps between the sprocket and chain will become smaller and that the chain will separate from the teeth of the sprocket.
A bicycle crank assembly comprises a crank arm and a sprocket. Among such bicycle crank assemblies, one known example is one in which a plurality of sprockets having different numbers of teeth are mounted to the crank arm. The sprockets are provided for shifting, and the chain is moved by a derailleur between the two sprockets having different numbers of teeth to perform the shifting action.